The contamination of the earth, including the soil and groundwater, by toxic chemicals from leaky storage vessels is now recognized as a serious problem. The only accepted solution to eliminate ground pollution from leaky storage vessels is to provide 100% primary containment and 100% of secondary containment. Many new tanks are provided with secondary containment by using a double-walled tank with a space between the inner and outer vessels. By monitoring the space between the inner (primary containment) and outer (secondary containment) vessels, a leak in the inner vessel (which destroys secondary containment) can be detected to allow the inner vessel to be drained.
U.S. Pat. No. 4,408,628 to Monk shows a method intended to repair leaky storage tanks. This patent provides a solution based on the premise that the in-place repair of leaky tanks with glass fiber resins or the like has not been accepted for hazardous materials. Monk proposes the use of an inflatable bladder to be placed in the tank. The tank would have a large manhole-like main access opening cut in its top with the various tank openings, such as fill, pump and vapor recovery for gasoline storage tanks, relocated to the main access opening. The bladder has a single opening connected to the access opening and fills up and collapses according to the fluid level within the bladder. The space between the bladder and existing tank is monitored to determine if anything leaks. Although Monk may provide a solution to leaky tanks in certain circumstances, it does not repair the tank, nor does it provide true 100% secondary containment system as is being mandated by law for new hazardous material storage vessels. Further, the entire bladder hangs from the access opening when the bladder is empty. This puts a great stress on the bladder fabric which can lead to early failure.